Sunday, August 7, 2011

Wapiti River Fieldwork, part 2

Here's a few more shots from the University of Alberta's fieldwork at the Wapiti River bonebed near Grande Prairie. Fieldwork wrapped up on Friday and the fossils are now at the U of A awaiting preparation.

It continues to amaze me just how much we have cleared out of this ledge over the last five years - when we started, the ledge did not exist.

I've learned that different field crews use different methods for mapping quarries. At the U of A, we use a baseline, grid square, plumb-bob and gridded paper to mark the location and orientation of bones in the quarry. (Sometimes it gets a little crowded, but people's heads make good supports for the grid square.) The grid square is a square meter, divided into 10x10 cm quadrants. The baseline is marked at 1 m increments along its length, and the grid square is lined up at the relevant marks. If the grid square is very high above the elements you want to map, a plumb-bob is useful for reducing parallax error. Each bone is marked with quarry coordinates, and eventually all of the map sheets are combined in photoshop or illustrator. The maps will help us to understand the taphonomy of the site.

We almost never find teeth at this site, but this year we recovered 2 or 3 ceratopsian teeth and 2 or 3 tyrannosaurid teeth. Here's one of the ceratopsian teeth, which you can see as a small triangle in the middle of the orange splotch.

Here's a Pachyrhinosaurus skull we helicoptered out on the second last day. It may not look like much, but I think this is one of the nicer ones we've gotten out of this quarry. You can see a large circle to the left that is probably the orbit. Because the block is already broken into smaller nodules, we jacketed the skull as multiple blocks to make arranging for the helicopter nets a little bit easier. The edges of all of the separate nodules were marked before jacketing so we can piece everything back together in the lab.